datatype¶

Canonical path: o6.datatype

datatype ¶

datatype(
    *,
    ns=None,
    nodeId=None,
    browseName=None,
    displayName=None,
    description=None,
    writeMask=None,
    userWriteMask=None,
    rolePermissions=None,
    accessRestrictions=0,
    isAbstract=False,
    defaultEncodingId=None,
    parent=None
)

Declare an OPC UA structure DataType from an annotated Python class.

The decorated class is a wire layout: every annotated attribute becomes a field of the type's StructureDefinition, and the layout is registered with open62541, so values encode and decode as a real structure instead of an opaque ExtensionObject. Python builtins map to their OPC UA counterparts, the sized o6 aliases pin an exact width, list[T] becomes a 1-D array of T, and another declared DataType nests as that type.

Python inheritance is the HasSubtype chain, so a subtype inherits its parent's fields. Deriving from ns0.datatypes.Union makes the StructureType a Union, in which assigning one field clears the previously selected one. As soon as one field is optional, the StructureType becomes StructureWithOptionalFields and unset optional fields read back as None. Per-field metadata that the annotation cannot express is attached with o6.field.

A user-supplied __init__, __repr__, and other methods are preserved; when they are absent, the native initializer and a field-listing repr are used.

Parameters:

Name	Type	Description	Default
`ns`	`Optional[str]`	Shortname of the declaring namespace. Inferred from `nodeId` when that carries a namespace, otherwise required.	`None`
`nodeId`	`Optional[str]`	NodeId of the DataType node. Allocated in the declaring namespace when omitted.	`None`
`browseName`	`Optional[str]`	BrowseName of the node. Defaults to the class name.	`None`
`displayName`	`Optional[str]`	DisplayName of the node. Defaults to the BrowseName.	`None`
`description`	`Optional[str]`	Description attribute. Defaults to the class docstring.	`None`
`writeMask`	`Optional[int]`	WriteMask attribute of the node.	`None`
`userWriteMask`	`Optional[int]`	UserWriteMask attribute of the node.	`None`
`rolePermissions`	`Optional[Mapping[Any, int]]`	RolePermissions, as a mapping of role to `o6.Permission` mask.	`None`
`accessRestrictions`	`int`	AccessRestrictions attribute of the node.	`0`
`isAbstract`	`bool`	Declare the structure abstract. It keeps a complete `DataTypeDefinition` for browsing clients but cannot be instantiated, and a field annotated with it is encoded as an `ExtensionObject` so it can carry any concrete subtype.	`False`
`defaultEncodingId`	`Optional[str]`	NodeId of the Default Binary encoding node. Allocated alongside the DataType when omitted.	`None`
`parent`	`Optional[Any]`	Node or declaration that owns the DataType node. Defaults to the `HasSubtype` parent implied by the Python base class.	`None`

Raises:

Type	Description
`TypeError`	The decorated object is not a class, the class has no annotated fields, or a field's rank cannot be represented as a structure member.

See @o6.datatype — structures.